There are over nine million dairy cows in the United States and Canada, and over twenty million worldwide. The dairy industry is a very competitive marketplace, and the pregnancy status of the herd is critical to maximizing profits. It is estimated that a non-pregnant cow costs the industry approximately five dollars per day. An accurate, rapid test for determining the pregnancy status of a herd would have a very important economic impact on ranch or farm operations and would increase milk production of the dairies, resulting in increased profitability for the dairies.
A number of antigens are known to be present in cows and sheep during pregnancy, and pregnancy has been evaluated by a variety of methods. Bovine Antigen Glycoprotein (U.S. Pat. No. 4,755,460, issued Jul. 5, 1988, and 4,895,804, issued Jan. 23, 1990) can be measured about 12-15 days after breeding. Early Pregnancy Factor (EPF) (U.S. Pat. No. 4,877,742, issued Oct. 31, 1989, and WO 00/51520, published Sep. 8, 2000) levels can be measured at about 20-40 days after breeding, such as with KEMS BioTest Ltd. (Littleton, Colo.) Animal Rapid Test for Bovine Pregnancy.
Interferon-tau is produced by bovine trophoblast tissue between days 15-24 of bovine gestation and prevents luteolysis by suppressing endometrial PGF2α secretion. Interferon-tau induces or upregulates expression of a number of proteins in pregnant animals.
Proteins that are induced by IFN-τ include granulocyte chemotactic protein (GCP-2) (WO 94/12537, published Jun. 9, 1994 and Staggs, K. L. et al. [1998] “Complex Induction of Bovine Uterine Proteins by Interferon Tau” Biol. Reprod. 59:293-297), 2′,5′-oligoadenylate synthetase (Short, E. C. et al. [2001] “Expression of antiviral activity and induction of 2′,5′-oligoadenylate synthetase by conceptus secretory proteins enriched in bovine trophoblast protein-1” Biol. Repro. 44:261-268), β2-microglobulin (Vallet, J. L. et al. [1991] “A low molecular weight endometrial secretory protein which is increased by ovine trophoblast protein-1 is a β2-microglobulin-like protein,” J. Endocrinology 130:R1-R4), IFN regulatory factors 1 (IRF-1) and 2 (IRF-2) (Spencer, et al. [1998] Biol. Reprod. 58:1154-1162; and Binelli M. et al. [2001] Biol. Reprod. 64(2):654-665), GCP-2 (Teixeira, M. G. et al. [1997] Endocrine 6:31-37); and 1-8U, 1-8D, and Leu-13/9-27 (Pru, J. K. et al. [2001] “Pregnancy and Interferon-τ Upregulate Gene Expression of Members of the I-8 Family in the Bovine Uterus” Biol. Reprod. 65:1471-1480; and Pru, J. K. [2000] “Regulation of bovine uterine proteins and prostaglandin F2a release by interferon-tau” Ph.D. Thesis, University of Wyoming). Leu-13 is the name of the protein encoded by the 9-27 gene. Cyclooxygenase-2 (COX-2) (Xiao, C W et al. [1998] “Regulation of COX-2 and prostaglandin F2a synthase gene expression by steroid hormones and IFN-τ in bovine endometrial cells,” Endocrinol. 139:2293-2299 and Thatcher, W. W. et al. [2001] “Uterine-conceptus Interactions and Reproductive Failure in Cattle” Theriogenology 56:1435-1450) and PLA2 (Binelli, M. et al. [2000] “Interferon-tau modulates phorbol ester-induced production of prostaglandin and expression of cyclooxygenase-2 and phospholipase-A2 from bovine endometrial cells” Biol. Repro. 63:417-424) are also regulated by IFN-τ.
Teixeira, M. G. et al. (1997) “Bovine Granulocyte Chemotactic Protein-2 is Secreted by the Endometrium in Response to Interferon-tau,” Endocrine 6(1):31-37 report that bovine 1-8 transcripts were detected on Days 15 and 18 of pregnancy and were absent on Day 12 of pregnancy and during the estrus cycle. Bovine 1-8 gene family members are not known to be secreted. This reference also reported that polyclonal antibodies to a GCP-2 peptide were generated in sheep, and used to demonstrate that GCP-2 is secreted by cultured endometrial cells, representing Day 14 of the estrus cycle, when dosed with IFN-τ.
Mx encodes a monomeric GTPase and is induced by IFN-τ (Ott, T. L. et al. [1998] “Effects of the Estrous Cycle and Early Pregnancy on Uterine Expression of Mx Protein in Sheep (Ovis aries)” Biol. Reprod. 59:784-794). In Ott et al. (1998), ovine Mx protein was detected using a monoclonal antibody directed against the amino terminus of human MxA (1319.35.126, supplied by M. Horisberger, Novartis, Basel Switzerland) and a Super ABC Mouse/Rat Kit (Biomeda, Foster City Calif.). U.S. Patent Applications No. 60/299,553 and 10/166,929 describe a method of determining pregnancy status of an animal by assaying the level of Mx and comparing it to the level of Mx in a non-pregnant animal. Mx protein was detected with ovine Mx peptide antiserum (#90618-2). Yankey, S. J. et al. (2001) “Expression of the antiviral protein Mx in peripheral blood mononuclear cells of pregnant and bred, non-pregnant ewes” J. of Endocrinology 170:R7-R11, describes the presence of Mx in peripheral blood mononuclear cells of pregnant ewes at Day 15 of pregnancy. Mx protein can also be used to detect viral infection (EP 0 725 081, published Aug. 7, 1996) using monoclonal antibodies to human Mx. Antibodies to human Mx and immunoassays for Mx have been described (Staeheli, P. and Haller, O. [1985] “Interferon-induced human protein with homology to protein Mx of Influenza virus-resistant mice” Mol. Cell. Biol. 5(8):2150-2153; Towbin H. et al. [1992] “A Whole Blood Immunoassay for the Interferon-Inducible Human Mx Protein” J. Interferon Res. 12(2):67-74; U.S. Pat. No. 5,869,264, issued Feb. 9, 1999; 5,739,290, issued Apr. 14, 1998; and U.S. Pat. No. 6,180,102 issued Jan. 30, 2001). Antibodies to mouse Mx are described in Staeheli, P. et al. (1985) Mol. Cell. Biol. 5:2150-2153; Staeheli, P. et al. (1985) J. Biol. Chem. 260(3):1821-1825; and Horisberger, M. A. et al. (1985) J. Biol. Chem. 260(3):1730-1733. One of the monoclonal antibodies in Towbin (1992) is reported to react with other species' Mx proteins (mouse, rat, bovine, and porcine), in addition to human Mx.
Another IFN-τ-induced protein is ubiquitin cross-reactive protein (UCRP), which was first identified in humans (Farrell, P. J. et al. [1979] Nature 279:523-525) and later characterized (Koran, B. D. [1984] “Interferon-induced Proteins” J. Biol. Chem. 259(23):14835-14839; Blomstrom, D. C. et al. [1986] J. Biol. Chem. 261:8811-8816; and Knight E. Jr. et al. [1988] J. Biol. Chem. 263:4520-4522). Human UCRP (hUCRP) and mouse UCRP encode proteins that are processed to 17 kDa but that migrate as 15 kDa on PAGE gels (Potter, J. L. et al. [1999] “Precursor processing of pro-ISG15/UCRP, an interferon-beta-induced ubiquitin-like protein” J. Biol. Chem. 274:25061-25068). These proteins are similar to ubiquitin, and are upregulated by interferon (IFN), hence they are also known as interferon-stimulated gene 15 (ISG15). ISG15 is involved in the viral response and in the recognition of pregnancy (Bebington, C. et al. [1999] “Localization of Ubiquitin and Ubiquitin Cross-Reactive Protein in Human and Baboon Endometrium and Decidua During the Menstrual Cycle and Early Pregnancy” Biol. Reprod. 60:920-928, and Bebington, C. et al. [1999] “Ubiquitin Cross-Reactive Protein Gene Expression is Increased in Decidualized Endometrial Stromal Cells at the Initiation of Pregnancy” Molecular Human Reproduction 5(10):966-972). Like ubiquitin, ISG15 becomes covalently attached to targeted intracellular proteins via a C-terminal LRGG amino acid sequence. Proteins that are coupled to ubiquitin often are degraded through the 26 S proteasome (Baboshina, O. V. [1996] “Novel multiubiquitin chain linkages catalyzed by the conjugating enzymes ESEPF and RAD6 are recognized by 26 S proteasome subunit 5,” J. Biol. Chem. 271:2823-2831). Ubiquitin is conjugated to other proteins by E2-conjugating enzymes (Tanaka, K. et al. [1998] “The ligation systems for ubiquitin and ubiquitin-like proteins” Mol. Cell. 8:503-512).
The 17 kDa bovine analog of hUCRP (ISG15) was identified as bovine UCRP (bUCRP) or ISG17 (Austin, K. J. et al. [1996] “Ubiquitin Cross-Reactive Protein is Released by the Bovine Uterus in Response to Interferon During Early Pregnancy,” Biol. Reprod. 54:600-606; Austin, K. J et al. [1996] “Complementary Deoxyribonucleic Acid Sequence Encoding bovine Ubiquitin Cross-Reactive Protein,” Endocrine 5(2):191-197; and Perry, D. J. et al. [1999] “Cloning of Interferon-Stimulated Gene 17: The Promoter and Nuclear Proteins That Regulate Transcription,” Molecular Endocrinology 13:1197-1206). ISG17 becomes covalently linked to targeted intracellular proteins, is released from endometrial cells, and may function as a paracrine modulator. Unlike ISG15, ISG17-conjugated proteins continue to accumulate rather than be degraded. Two of the 1-8 gene family members, bovine 1-8U and bovine Leu-13, have high homology with the E2-conjugating enzymes, and they retain critical amino acids for function. It has been suggested that they may function by conjugating ISG17 to proteins.
A normal bovine estrus cycle is about 21 days in length. ISG17 has been detected by Day 15 of pregnancy. It continues to increase to Day 17, and remains high through Day 26 (Hansen, T. R. et al. [1997] “Transient Ubiquitin Cross-Reactive Protein Gene Expression in the Bovine Endometrium,” Endocrinology 138(11):5079-5082; and Spencer, T. E. et al. [1999] “Differential Effects of Intrauterine and Subcutaneous Administration of Recombinant Ovine Interferon Tau on the Endometrium of Cyclic Ewes,” Biol. Reprod. 61:464-470). ISG17 was not detectable above background during the estrus cycle of non-pregnant bovine.
One ISG17 function is to become cross-linked to cellular proteins, as does ubiquitin. Conjugation of ISG17 to endometrial cytosolic proteins was observed by Western Blotting using a polyclonal antibody to an ISG17 polypeptide (Johnson, G. A. et al. [1998] “Pregnancy and Interferon-Tau Induce Conjugation of Bovine Ubiquitin Cross-Reactive Protein to Cytosolic Uterine Proteins,” Biol. Reprod. 58:898-904). The peptide used to generate the polyclonal antibodies corresponds to amino acids 82 to 99 of ISG17. This polypeptide was chosen because it had a high antigenic index, 78% identity with ISG15, and low identity (22%) with ubiquitin. Attempts to use the antiserum to develop a pregnancy test met with limited or no success (Pru, J. K. [2000] “Regulation of bovine uterine proteins and prostaglandin F2a release by interferon-tau” Ph.D. Thesis, University of Wyoming, Appendix 1, page 1). Another antibody which has been utilized in the study of ISG17 is monoclonal antibody 5E9 (Pru, J. K. [2000] “Regulation of bovine uterine proteins and prostaglandin F2a release by interferon-tau” Ph.D. Thesis, University of Wyoming, Appendix 1).
The Johnson polyclonal antibody to ISG17 amino acids 82-89 was also used to study ISG17 induction by IFN-τ by Western blotting (Staggs, K. L. et al. [1998] “Complex Induction of Bovine Uterine Proteins by Interferon Tau,” Biol. Reprod. 59:293-297).
ISG17 also can induce expression of IFN-τ in peripheral blood mononuclear cells (PMBCs) (Pru, J. K. et al. [2000] “Production, Purification, and Carboxy-Terminal Sequencing of Bioactive Recombinant Bovine Interferon-Stimulated Gene Product 17,” Biol. Reprod. 63:619-628).
Ovine UCRP (oUCRP) has been cloned (Charleston, B. and Stewart, H. J. [1993] “An interferon-induced Mx protein: cDNA sequence and high level expression in the endometrium of pregnant sheep,” Gene 137:327-331). Ovine UCRP is reported to be detectable by Day 13, and to remain high through Day 19 of ovine pregnancy (Johnson, G. A. et al. [1999] “Expression of the Interferon Tau Inducible Cross-Reactive Protein in the Ovine Uterus,” Biol. Reprod. 61:312-318). Western blotting of oUCRP was performed using a polyclonal antibody to human UCRP.
Other factors, in addition to IFN-τ, may be responsible for the induction of UCRP (Johnson, G. A. et al. [2000] “Interferon-tau and Progesterone Regulate Ubiquitin Cross-Reactive Protein Expression in the Ovine Uterus,” Biol. Reprod. 62:622-627).
Estrone sulfate was found to be increased around day 50 in bovine peripheral blood. (Hirako, M. and Takahashi, H. [2000], “Oestrone sulfate commences an increase around 50 days of gestation in bovine peripheral blood,” Reprod. Fertil. Dev. 12(7-8):351-354.) Estrone sulfate analysis in urine or serum after Day 100 has also been used to confirm pregnancy (Holdsworth et al. [1982] J. Endocrin. 95:7-12 and Warnick et al. [1995] Theriogenol. 44:811-825).
PSP60 is disclosed in Mialon, M. M., et al. (1993), “Peripheral concentration of a 60-kDa pregnancy serum protein during gestation and after calving and in relationship to embryonic mortality in cattle,” Reprod. Nutr. Dev. 33(3):269-82, to be present in peripheral blood from day 27 after artificial insemination until and beyond the end of pregnancy. Mialon, M. M., et al. (1994), “Detection of pregnancy by radioimmunoassay of a pregnancy serum protein (PSP60) in cattle,” Reprod. Nutr. Dev. 34(1):65-72 discloses that testing 349 cows for PSP60 28, 35, 50 and 90 days post-insemination gave accurate results compared with other known tests. Patel, O. V., et al. (1998), “Effect of stage of gestation and foetal number on plasma concentration of a pregnancy serum protein (PSP-60) in cattle,” Res. Vet. Sci. 65(3):195-199 discloses that PSP60 increased from day 20 post-oestrus to 20 days pre-partum.
Pregnancy-associated glycoprotein 1 (PAG-1) is disclosed in Xie, S., et al. (1991), “Identification of the major pregnancy-specific antigens of cattle and sheep as inactive members of the aspartic proteinase family,” Proc. Nat'l Acad. Sci. USA 88(22):10247-10251. This article teaches that pregnancy in cattle and sheep can be diagnosed by the presence of this conceptus-derived antigen in maternal serum. Zoli, A. P., et al. (1992), “Radioimmunoassay of a bovine pregnancy-associated glycoprotein in serum: its application for pregnancy diagnosis,” Biol. Reprod. 46(1):83-92 discloses a double-antibody radioimmunoassay for bovine PAG-1 which was detected in maternal peripheral blood beginning at day 22 of pregnancy and increasing progressively to day 270, and becoming undetectable by day 100 postpartum. Xie, S. et al. (1997), “The diversity and evolutionary relationship of the pregnancy-associated glycoproteins, an aspartic proteinase subfamily consisting of many trophoblast-expressed genes,” Proc. Nat'l Acad. Sci. USA 94(24):12809-12816, teaches that cattle, sheep and probably all ruminant artiodactyla possess up to 100 or more pregnancy-associated glycoprotein genes, many of which are placentally expressed. Szenci, O. et al. (1998), “Evaluation of false ultrasonographic diagnoses in cows by measuring plasma levels of bovine pregnancy-associated glycoprotein 1,” Vet. Rec. 142(12):304-306 taught that this antigen showed that before day 31 ultrasonographic scanning was not very sensitive because six of the 30 calving cows were incorrectly diagnosed as non-pregnant. 0.5 ng/ml was used as the cut-off point to determine pregnancy. Pregnancy Associated Glycoproteins (PAGs) can also be detected during early pregnancy (WO 99/47934, published Sep. 23, 1999). Szenci, O. et al. (1998) “Comparison of Ultrasonography, Bovine Pregnancy-Specific Protein B, and Bovine Pregnancy-Associated Glycoprotein 1 Tests for Pregnancy Detection in Dairy Cows” Theriogenology 50:77-88, describes a comparison of bovine pregnancy tests for days 26 to 58 after artificial insemination (AI). Green, J. et al. (2000), “Pregnancy-associated bovine and ovine glycoproteins exhibit spatially and temporally distinct expression patterns during pregnancy,” Biol. Reprod. 62(6): 1624-1631, discloses that pregnancy-associated glycoproteins in sheep and cows are expressed in the trophectoderm or binucleate cells. Those expressed predominantly in bovine binucleate cells are expressed weakly if at all by day 25 placenta, but are present at the middle and end of pregnancy. Others, such as PAG-4, -5 and -9 are present at Day 25 and at earlier stages. Roberts, R. M., et al. (1995), “Glycoproteins of the aspartyl proteinase gene family secreted by the developing placenta,” Adv. Exp. Med. Biol. 362:231-240, teaches that pregnancy in cattle and sheep can be diagnosed by the presence of placentally-derived antigens (pregnancy-associated glycoproteins or PAG-1) in maternal serum soon after implantation begins at about day 20 following conception.
Pregnancy-specific Protein B (PSPB) is disclosed in U.S. Pat. No. 4,554,256, issued Nov. 19, 1985; 4,705,748, issued Nov. 10, 1987; European Patent No. 0132750, published Feb. 13, 1985; and Sasser, R., et al. (1986), “Detection of pregnancy by radioimmunoassay of a novel pregnancy-specific protein in serum of cows and a profile of serum concentrations during gestation,” Biol. Reprod. 35(4):936-942. Serum concentrations of PSPB exceeded 1 ng/ml by 30 days post-breeding and increased gradually through three months, six months, and nine months of gestation, declining steadily to less than 78 ng/ml by 21 days postpartum. PSPB could be measured in most cows by 24 days after breeding. Szenci, O. et al. (1998), “Comparison of ultrasonography, bovine pregnancy-specific protein B, and bovine pregnancy-associated glycoprotein 1 tests for pregnancy detection in dairy cows,” Theriogenology 50(1):77-88, teaches that at days 26 to 58 after artificial insemination, pregnancy testing with PSPB diagnosed pregnant cows as accurately as measuring of PAG-1 or ultrasound; however, there were fewer false positive diagnoses with the PSPB test than the PAG-1 test. PSPB has also been tested in llamas (Drew, M. I. et al. [1995] “Pregnancy determination by use of pregnancy-specific protein B radioimmunoassay in llamas” JAVMA 207(2):217-219); deer (Willard, S. T. et al. [1998] “Early pregnancy detection and the hormonal characterization of embryonic-fetal mortality in fallow deer” Theriogenology 49:861-869); and sheep (Willard, J. M. et al. [1995] “Detection of fetal twins in sheep using a radioimmunoassay for PSPB” J. Anim. Sci. 73:960-966) for detection of twins. PSPB is also detectable after calving (Kiracofe, G. H. et al. [1993] “PSPB in serum of postpartum beef cows” J. Anim. Sci. 71:2199-2205). Polyclonal antibodies against PSPB are described in U.S. Pat. No. 4,705,748 and Humblot et al. (1988), “Pregnancy-specific protein B, progesterone concentrations and embryonic mortality during early pregnancy in dairy cows,” Reprod. Fertil. 83(1):215-223.
Progesterone is an antigen which is present throughout pregnancy. Progesterone levels have been measured in milk or blood samples collected from cattle after 22-24 days, such as offered at Rocky Mountain Instrumental Laboratories Inc. (Fort Collins, Colo.), but measurements of progesterone in milk at days 18-22 yield unacceptably high rates of false positives (Oltenacu et al. [1990] J. Dairy Sci. 73:2826-2831 and Markusfeld et al. [1990] Br. Vet. J. 146:504-508). Moriyoshi, M. et al. (1996), “Early pregnancy diagnosis in the sow by saliva progesterone measurement using a bovine milk progesterone qualitative test EIA kit,” J. Vet. Med. Sci. 58(8):737-741 discloses that pregnancy could be diagnosed 17-24 days after last mating in sows. Polyclonal antibodies to progesterone are commercially available from many different sources including Research Diagnostics, Inc., Flanders, N.J., and are described in Humblot, F., et al. (1988) “Pregnancy-specific protein B., progesterone concentrations and embryonic mortality during early pregnancy in dairy cows,” Reprod. Fertil. 83(1):215-223. Monoclonal antibodies to progesterone are available commercially through OEM Concepts, Tom's River, N.J.
Johnson, G. A. et al. (1998) “Pregnancy and Interferon-Tau Induce Conjugation of Bovine Ubiquitin Cross-Reactive Protein to Cytosolic Uterine Proteins,” Biol. Reprod. 58:898-904, discloses polyclonal antibodies to ISG17. The peptide used to generate the polyclonal antibodies corresponds to amino acids 82 to 99 of ISG17, LVRNDKGRSSPYEVQLKQ. This polypeptide was chosen because it had a high antigenic index, 78% identity with ISG15, and low identity (22%) with ubiquitin. Attempts to use the antiserum to develop a pregnancy test met with limited or no success (Pru, J. K. [2000] “Regulation of bovine uterine proteins and prostaglandin F2a release by interferon-tau” Ph.D. Thesis, University of Wyoming, Appendix 1, page 1). Another antibody which has been utilized in the study of ISG17 is monoclonal antibody 5E9 (Pru, J. K. (2000) “Regulation of bovine uterine proteins and prostaglandin F2a release by interferon-tau” Ph.D. Thesis, University of Wyoming, Appendix 1). U.S. Patent Application 60/393,615 discloses cDNAs believed to be associated with early bovine pregnancy.
Prior bovine pregnancy tests have tested only single antigens. However, false positives may occur when single antigens are tested, since positive test results may occur for these antigens when certain viruses are present. Some antigens such as progesterone are present in lactating cows. Thus a test is needed which will reliably determine bovine pregnancy with minimal false positive results.
Methods of making assay devices are described in Millipore's Short Guide for Developing Immunochromatographic Test Strips (2nd ed). Other assay devices and methods are described in U.S. Pat. Nos. 4,313,734, 4,376,110, 4,435,504, 4,486,530, 4,703,017, 4,740,468, 4,855,240, 4,954,452, 5,028,535, 5,075,078, 5,137,808, 5,229,073, 5,591,645, 5,654,162, 5,798,273, and in EP 0810436A1, and WO 95/16207. Assay devices containing more than one test strip are described at the Unitec, Inc. website.
In cows, the estrus cycle is about 21 days. To determine when a cycling cow is ready for breeding, the cow can be observed for behavioral estrus. Alternatively, a cow can be induced or forced into estrus with effective hormone therapies. Estrus of an entire herd can be synchronized (U.S. Patent Nos. 3,892,855 issued Jul. 1, 1975, and 4,610,687 issued Sep. 9, 1986). Estrus synchronization, or preferably ovulation synchronization, is used in timed AI (TAI) breeding programs. TAI breeding programs involve precise estrus synchronization which allows for timed breeding without monitoring for behavioral estrus. Examples of methods for forcing estrus include U.S. Pat. No. 5,589,457 (issued Dec. 31, 1996), Ovsynch (Pharmacia Animal Health, Peapack, N.J.), Cosynch, Select Synch, Modified Select Synch, MGA/PGF, and Syncro-Mate-B. Such methods typically employ hormones such as prostaglandins, e.g. PGF2α (Lutalyse®, Pharmacia Upjohn, Peapack, N.J.; Bovilene®, Syntex; Animal Health, Des Moines, Iowa; and Estrumate® Haver Lockhart, Shawnee, Kans.), and gonadotropin-releasing hormone (GnRH). Ovsynch involves a GnRH injection followed by a prostaglandin injection one week later, followed by a second GnRH injection 48 hours later. Insemination is ideally then performed at 12-18 hours, preferably about 16 hours, after the second GnRH injection. Ovsynch is maximally effective when implemented between Days 18-20 of a 20-day bovine estrus cycle (Thatcher, W. W. et al. [2000] “New Strategies to Increase Pregnancy Rates” at the website nab-css.org/education/Thatcher.html Presynch (Pharmacia Animal Health, Peapack, N.J.) can be used to synchronize heifers before implementing Ovsynch. Presynch involves two prostaglandin injections. Some of the above-mentioned methods are also used on non-cycling cows to induce cycling, such as in lactating dairy cows. After precise estrus synchronization, animals need not be monitored for behavioral estrus and may be bred by appointment. Some animals may need estrus presynchronization before estrus synchronization. Melengestrol acetate (MGA™) in feed (Imwalle, D. B. et al. (1998) “Effects of melengestrol acetate on onset of puberty, follicular growth, and patterns of luteinizing hormone secretion in beef heifers” Biol. Repro. 58:1432-1436) or implants (U.S. Patent Publication No. 2001/0041697, published Nov. 15, 2001) can be used for presynchronizing estrus in heifers. Resynch is a program whereby animals are synchronized and bred, and then those animals that are determined to be open (not pregnant) are again synchronized and rebred.
Prostaglandin alone has been administered sequentially or simultaneously with artificial insemination to reduce the number of insemination administrations per herd required for achieving pregnancy (WO 02/04006, published Jan. 17, 2002).
Prostaglandin can be used as a single injection. An injection of about 2-5 cc of Lutalyse (prostaglandin PGF2α) will induce an animal with a mature corpus luteum to come into estrus in about 48-96 hours. Cattle typically have a functional corpus luteum during Days 5-18 of the cycle (Estrus Synchronization of Cattle, Publication F-3163, Oklahoma Cooperative Extension Service, Oklahoma State University). Animals induced into estrus can be bred at 2-5 days following a prostaglandin injection. Single injection prostaglandin programs are often used with estrus synchronization, corpus luteum palpation, or behavioral heat detection because only animals in certain stages of the estrus cycle will respond by going into estrus. Breeding by appointment with a standard prostaglandin program has not been recommended because the interval from injection to estrus varies depending on the stage of the cycle when prostaglandin is administered. For example, if a cow is at cycle Day 7-8 or Day 15-17, timed AI can be performed at about 72-80 hours after the injection (O'Connor, M. L. discussion found at the website inform.umd.edu/EdRes/Topic/AgrEnv/ndd/reproduce and das.psu.edu/reproduction/check/pdf/synchron.pdf). A risk of using prostaglandin injection for forcing estrus is that prostaglandin can cause abortion when given to pregnant animals. Estrus and ovulation synchronization allows cattle managers to concentrate heat detection efforts in a relatively short period of time or allows for TAI, which requires no heat detection (see the website ianr.unl.edu/beef/g741.htm).
There is a need in the art to determine pregnancy status during the breeding of livestock. In cattle, conception rates are low (Streenan and Diskin, Eds. [1986] Embryonic Mortality in Farm Animals, Martinus Nijhoff Publishers, 1-11) and spontaneous abortion rates are high, making pregnancy/non-pregnancy determination and rebreeding/inseminating important management tools. Particularly there is a need to determine pregnancy/non-pregnancy status during the estrus cycle in which insemination occurs or the first estrus cycle after insemination so that animals that are not pregnant can be most economically rebred. This need is particularly strong when raising livestock such as cattle, especially on dairy farms.
There is a need in the art for tests that determine pregnancy, and particularly non-pregnancy, status of animals during the estrus cycle in which insemination occurs or during the first estrus cycle after insemination. Knowing which animals are non-pregnant allows efforts to be directed towards forcing non-pregnant animals into estrus and/or watching for signs of estrus, in preparation for insemination, to decrease the time an animal is not pregnant. Pregnancy is dependent, not only on conception/fertilization but also on maternal recognition of pregnancy during the critical period, which allows for implantation. Up to 40% of total embryonic losses are estimated to occur between Days 8 and 17 of pregnancy in cattle (Thatcher, W. W. et al. [1994] “Embryo Health and Mortality in Sheep and Cattle,” J. Anim. Sci. 72(Suppl. 3):16-30). In the absence of reliable pregnancy tests, the earliest time at which a non-pregnant animal can be identified is at the beginning of a new estrus cycle, by observation of behavioral estrus. Optimally, pregnancy/non-pregnancy status is determined towards the end of or after the critical period when pregnancy is maintained, Days 15-17 according to Binelli, M. et al. (2001) “Antiluteolytic Strategies to Improve Fertility in Cattle,” Theriogenology 56:1451-1463, but before the end of the first estrus cycle, Days 18-20, allowing timed artificial insemination programs to be maximally effective. This reference discloses that pregnancy/non-pregnancy status is optimally determined during Days 17-18.
Additional technology relating to pregnancy testing in cows and other animals is disclosed in U.S. Provisional Patent Application Nos. 60/377,987, 60/377,166, 60/380,043, 60/377,921, 60/377,165, 60/377,355, 60/377,829, and 60/380,042, all filed May 2, 2002.
All references cited herein are incorporated herein by reference in their entirety to the extent that they are not inconsistent with the disclosure herein. Citation of the above documents is not intended as an admission that any of the foregoing is pertinent prior art. All statements as to the date or representation as to the contents of these documents is based on subjective characterization of the information available to the applicant, and does not constitute any admission as to the accuracy of the dates or contents of these documents.